The present disclosure relates to an image reading device having an automatic document sheet reading function, and in particular relates to an adjustment mechanism and an adjustment method for adjusting a distance between a transparent plate member and a reading portion, wherein the transparent plate member is an elongated plate and is in contact with a reading surface of the document sheet when the document sheet is moved during an automatic document sheet reading.
The image reading device is provided with a reading portion that includes a reading sensor such as a CIS in which a plurality of imaging elements are arranged in a main scanning direction, a light-emitting element such as an LED that irradiates light toward an imaging target, and optical parts such as a lens and a mirror. Conventionally, in an image reading device having an automatic document sheet reading function, a document sheet is read in such a manner that the reading portion is disposed below a contact member (transparent plate member) that is in the shape of an elongated plate, and then the document sheet is moved in the state where a reading surface of the document sheet faces the upper surface of the contact member. This allows an image on the reading surface to be read while the document sheet is moving.
In addition, the image reading device is provided with a document sheet table glass on which the document sheet is placed such that an image is read from the document sheet in a stationary state. As an example of this type of image reading device, there is known a device in which the document sheet table glass is supported in such a manner that the height of the center of the document sheet table glass between support points can be adjusted by adjustment screws.